When illuminating the space underneath a ceiling or a canopy, it is often required to direct the light radiation in such a way that light beams having a large angle of, for example, more than 60° with respect to the vertical direction are reduced or even completely blocked in order to avoid glare, i.e. bright light radiation dazzling persons at some distance from the location of the luminaire. In particular when the luminaire illuminates the space underneath the canopy of a petrol station or a space in which persons move in a preferential direction, glare has to be avoided in this direction, while it may be required to illuminate one or two side walls parallel to this preferential direction of movement. For example, such a space is also present in a tunnel through which people are walking or driving in cars.
Publication U.S. Pat. No. 7,252,412 describes such a luminaire for illuminating the space underneath a canopy of a petrol station. Glare dazzling drivers entering the petrol station is avoided with this luminaire, but light radiation in the transverse direction for illuminating the vertical surfaces of the petrol pumps has to be directed at relatively large angles to the vertical direction. The petrol pumps may be located on one or both sides of the driveway through the petrol station. If the petrol pumps are present on only one side of the driveway through the petrol station, the luminaire should only illuminate that side, whereas light radiation to the other side should be avoided, in particular when the road along which the petrol station is located is on this other side. Furthermore, it is desired to limit the light radiation in order to avoid waste of energy, i.e. to avoid light radiation outside the space underneath the canopy.
In order to avoid glare, the luminaire can be provided with louvers for blocking light radiation in certain directions. In order to increase or decrease the intensity of the light radiation in certain other directions, the luminaire can be provided with one or more light-reflecting surfaces having a specific shape, so that the light radiation is reflected to predetermined directions. Such a luminaire has the drawback of loss of effective light radiation emitted by the luminaire, so that a surplus of electric power is required.
When making use of LEDs in combination with refractive optics, i.e. a lens, a relatively efficient luminaire can be obtained, producing bright illumination with relatively low electric power supply. Such a luminaire is described in EP-A-1758068. This publication discloses an elongated luminaire provided with an elongated lens extending parallel to the array of LEDs, in which the array of LEDs and the lens have a common longitudinal plane of symmetry. The luminaire has an elongated U-shaped body whose bottom is provided with the straight array of LEDs. The elongated lens is clamped between the legs of the U-shaped body in order to obtain the desired light radiation emitted by the luminaire.